Wind-dispersed Pollen Research Articles

Cloud condensation nuclei activation properties of Mediterranean pollen types considering organic chemical composition and surface tension effects

Wind-dispersed pollen grains emitted from vegetation are directly injected into the atmosphere being an important source of natural aerosols globally. These coarse particles of pollen can rupture into smaller particles, known as subpollen particles (SPPs), that may act as cloud condensation nuclei (CCN) and affect the climate. In this study, we characterize and investigate the ability of SPPs of 10 Mediterranean-climate pollen types to activate as CCN. A continuous flow CCN counter (CCNC) was used to measure the activation of size-selected (80, 100 and 200 nm dry mobility diameter) particles at different supersaturations (SS). Hygroscopicity parameter (κ) for each SPP type and size has been calculated using κ-Köhler theory. Organic chemical speciation and protein content has been determined to further characterize pollen solutions. Furthermore, the surface activity of SPPs has also been investigated by using pendant drop tensiometry. All studied SPP samples show critical supersaturation (SSCrit) values that are atmospherically relevant SS conditions. Hygroscopicity κ values are in the range characteristic of organic compounds (0.1–0.3). We found that organic speciation and protein content vary substantially among pollen types, with saccharides and fatty acids being the only organic compounds found in all pollen types. A clear relationship between SPP activation and its organic composition was not observed. This study also reveals that all SPPs investigated reduce the surface tension of water at high concentrations but at diluted concentrations (such as those of activation in the CCNC), the water surface tension value is a good approximation in Köhler theory. Overall, this analysis points out that pollen particles might be an important source of CCN in the atmosphere and should be considered in aerosol-cloud interactions processes.

Transgenic plants — a threat to local flora?

The paper covers major threats associated with wide-range introduction and cultivation of transgenic plants due to germplasm mixing with that of indigenous species of natural plant communities and risks of transgenic plants adverse impact on the environment. Among them are: influencing non-target species, invasive power, possibility of GMPs escaping into the environment by horizontal gene transfer as well as harmful effect on the soil biota.
 Currently, herbicide- and pest-resistant genetically modified plants (GMP) became an integral part of contemporary agrotechnologies in many economies [1]. However, most countries lack national strategy providing science-based substantiated procedure of creating, distribution and safe production of GMP. Rapid development of agricultural biotechnology and GMP production offered many economical benefits but also caused concern due to their potential environmental impact. To date, truly negative effects of GMP production, revealed in the course of growing, are known: harmful effect of entomocide Cry-proteins (Bt endotoxins) on non-target biota, target phytophage resistance to insecticidal plants, phytophage species succession to replace the species eliminated in the agrocoenosis. Vertical transfer of GMP transgenes (repollination between transgenic plants and wild species or isogenic varieties), as well as slow decomposition of transgenic plants remains all these factors can have remote environmental consequences [2, 3]. Wind-dispersed pollen of insecticidal GMP contaminates soil and open water reservoirs by toxins, thus posing potential hazards for aquatic organisms and geobionts (including rhizospheric organisms).
 Thus, uncontrolled GMP production and introduction, creates a real threat of losing biodiversity and genetic diversity of indigenous plants due to biological contamination. Therefore, GMP cultivation and monitoring in the fields is of exceptional importance and must be regulated by a science-based national strategy. This strategy would allow to exclude agroecological and environmental genetic risks, to keep the genetic diversity of natural plant communities.

Insights Into the Significance of the Chinense Loess Plateau for Preserving Biodiversity From the Phylogeography of Speranskia tuberculata (Euphorbiaceae).

The significance of the Chinese Loess Plateau (CLP) in maintaining biodiversity for northern China has rarely been shown, as previous phylogeographic studies are mostly woody species and they have revealed that Quaternary refugia are mainly located in mountain regions. We selected a drought-enduring endemic herb, Speranskia tuberculata (Euphorbiaceae), to determine its glacial refugia and postglacial demographic history. To this end, we sampled 423 individuals from 38 populations covering its entire geographic distribution. Three chloroplast DNA (cpDNA) fragments, two low-copy nuclear genes, and six nuclear microsatellites (nSSRs) were used and supplemented with ecological niche modeling (ENM) to infer the phylogeographic history of this species. Populations with private haplotypes and high haplotype diversity of cpDNA are mainly located in the CLP or scattered around northeastern China and the coastal region. Spatial expansion, detected using a neutrality test and mismatch distribution, may have resulted in a widely distributed ancestral cpDNA haplotype, especially outside of the CLP. For nuclear DNA, private haplotypes are also distributed mainly in the CLP. In nSSRs, STRUCTURE clustering identified two genetic clusters, which are distributed in the west (western cluster) and east (eastern cluster), respectively. Many populations belonged, with little to no admixture, to the western cluster while (hardly) pure populations of the eastern cluster were barely found. Genetic differentiation is significantly correlated with geographic distance, although genetic diversity is uniformly distributed. ENM suggests that the distribution of S. tuberculata has recently expanded northwards from the southern CLP, whereas it has experienced habitat loss in the south. Thus, S. tuberculata populations probably survived the last glacial maximum (LGM) in the southern CLP and experienced post-glacial expansion. Wind-dispersed pollen could bring the majority of genotypes to the front during spatial expansion, resulting in uniformly distributed genetic diversity. Based on evidence from molecular data and vegetation and climate changes since the LGM, we conclude that drought-enduring species, especially herbaceous species, are likely to have persisted in the CLP during the LGM and to have experienced expansion to other regions in northern China.

Population isolation results in unexpectedly high differentiation in Carolina hemlock (Tsuga caroliniana), an imperiled southern Appalachian endemic conifer

Carolina hemlock (Tsuga caroliniana Engelm.) is a rare conifer species that exists in small, isolated populations within a limited area of the Southern Appalachian Mountains of the USA. As such, it represents an opportunity to assess whether population size and isolation can affect the genetic diversity and differentiation of a species capable of long-distance gene flow via wind-dispersed pollen and seed. This information is particularly important in a gene conservation context, given that Carolina hemlock is experiencing mortality throughout its range as a result of infestation by hemlock wooly adelgid (Adelges tsugae Annand), an exotic insect. In this study, 439 Carolina hemlock trees from 29 areas (analyzed as populations) were sampled, representing an extensive range-wide sampling of the species. Data from 12 polymorphic nuclear microsatellite loci were collected and analyzed for these samples. The results show that populations of Carolina hemlock are extremely inbred (F IS = 0.713) and surprisingly highly differentiated from each other (F ST = 0.473) with little gene flow (Nm = 0.740). Additionally, most populations contained at least one unique allele. This level of differentiation is unprecedented for a North American conifer species. Numerous genetic clusters were inferred using two different clustering approaches. The results clearly demonstrate that, existing as a limited number of small and isolated populations, Carolina hemlock has insufficient gene flow to avoid widespread genetic drift and inbreeding, despite having the capacity to disperse pollen and seed relatively long distances by wind. These results have important conservation implications for this imperiled species.

Holocene history of a raised bog, northern New Zealand, based on plant cuticles

We present a method for analysing subfossil plant cuticles preserved in peat and apply the method to provide a preliminary, coarse resolution reconstruction of Holocene vegetation history at Moanatuatua Bog, northern North Island, New Zealand. The plant cuticle record reveals the early-Holocene development of a swamp and its transition to a raised bog, which is not apparent from other proxies. Comparison with a pollen record from the same sequence highlights the advantages of plant cuticle analysis in cases where pollen is hard to identify or poorly preserved. In particular, distinguishing between the pollen grains of the two main bog species, the restiads Empodisma robustum and Sporadanthus ferrugineus, relies on subtle gradational characteristics, whereas their cuticular patterns are very distinct. Furthermore, Cyperaceae pollen is poorly preserved at Moanatuatua Bog, being almost completely absent, whereas the Cyperaceae cuticles are present throughout the sequence. Therefore, we suggest that Cyperaceae pollen at this site is a less reliable indicator of local sedge communities than the cuticle record. The wide dispersal capabilities of these wind-dispersed pollen types also make them less suitable for determining local site vegetation and environmental change in comparison with cuticle remains. These results suggest that plant cuticle analysis may be a useful tool for the reconstruction of long-term vegetation changes from peat sequences, especially when used in concert with palynology. Sample preparation also proved to be fast with little equipment or chemicals needed.

Modern pollen–vegetation relationships in saltmarsh habitats along a salinity gradient of a fluvial estuary

The classification of vegetated habitats and the palynological study of surface sediments are used to evaluate the plant-pollen relationship in the saltmarshes of the Chuí River (southern Brazil). The visual plant cover was recorded in five transects perpendicular to the river's margins and positioned along 4.5km of the estuarine gradient. Two-way Indicator Species Analysis (TWINSPAN) of the plant cover in 65 sampled quadrats was used to characterize five vegetated habitats. These habitats were distinguished by their elevation in the intertidal zone and their location in the estuarine gradient. The salinity of surface water that flooded low marshes decreased from 20 to 4 between transect 1 and transect 5. A total of 10 surface soil samples from marsh habitats were taken in the same transects as for the study of vegetation, and pollen and spores were identified. The pollen frequencies of dominant families (Cyperaceae, Poaceae, Chenopodicaeae, Juncaceae and Asteraceae) on the surface of marsh habitats show high correlations with the parent plant cover (0.66 to 0.81), but pollen taxa show a higher richness in the plant taxa. The most frequent spores (massulae) encountered in all samples belong to the aquatic fern Azolla filiculoides, followed by spores of the moss Phaeoceros. The palynological data obtained are consistent with the regional vegetation cover characteristics of saltmarshes, but it is difficult to distinguish different habitat types (Discriminant Analysis results). This low discrimination of pollen-spore assemblages is related to the widespread distribution of the indicator plant species, mostly taxa known to produce large quantities of (primarily) wind-dispersed pollen, which are also redeposited or transferred by tides or freshwater influxes. The low taxonomic resolution of pollen grains of dominant taxa, such as Cyperaceae and Poaceae, also creates difficulties to distinguish the vegetated marsh habitats based on pollen assemblages. The widespread presence of pollen from introduced plants such as Pinus species near the saltmarshes emphasizes the anthropogenic impact on this region.

Habitats, Trade Winds, and Pollination of the EndangeredCycas micronesica: Is There a Role for Wind as Pollen Vector on the Island of Guam?

Premise of research. The role of specialist insects in the pollination of cycads is well established, with wind playing little to no role. Questions remain for species within the Cycas rumphii complex that have dispersed via floating seeds to islands far from mainland ancestors. One such species, Cycas micronesica, resides in habitats on the island of Guam that are exposed to trade winds that enhance the potential for wind pollination.Methodology. We examined the distance and direction of horizontal pollen movement either from microstrobili or from experimentally released pollen relative to wind direction and velocity in several different Guam cycad habitats. Wind-dispersed pollen was also captured around megasporophylls and then examined relative to wind and distance from dehiscing microstrobili.Pivotal results. Wind velocity, trap direction, and trap distance from the pollen source were the most important factors affecting pollen capture. In habitats where C. micronesica grows in the deep understory wit...

Aerodynamics and pollen ultrastructure in Ephedra.

• Pollen dispersal is affected by the terminal settling velocity (Ut) of the grains, which is determined by their size, bulk density, and by atmospheric conditions. The likelihood that wind-dispersed pollen is captured by ovulate organs is influenced by the aerodynamic environment created around and by ovulate organs. We investigated pollen ultrastructure and Ut of Ephedra foeminea (purported to be entomophilous), and simulated the capture efficiency of its ovules. Results were compared with those from previously studied anemophilous Ephedra species.• Ut was determined using stroboscopic photography of pollen in free fall. The acceleration field around an "average" ovule was calculated, and inflight behavior of pollen grains was predicted using computer simulations. Pollen morphology and ultrastructure were investigated using SEM and STEM.• Pollen wall ultrastructure was correlated with Ut in Ephedra. The relative proportion and amount of granules in the infratectum determine pollen bulk densities, and (together with overall size) determine Ut and thus dispersal capability. Computer simulations failed to reveal any functional traits favoring anemophilous pollen capture in E. foeminea.• The fast Ut and dense ultrastructure of E. foeminea pollen are consistent with functional traits that distinguish entomophilous species from anemophilous species. In anemophilous Ephedra species, ovulate organs create an aerodynamic microenvironment that directs airborne pollen to the pollination drops. In E. foeminea, no such microenvironment is created. Ephedroid palynomorphs from the Cretaceous share the ultrastructural characteristics of E. foeminea, and at least some may, therefore, have been produced by insect-pollinated plants.

Invasive conifers reduce seed set of a native Andean cedar through heterospecific pollination competition

The invasion of natural forest communities by introduced woody species may threat processes that are critical for ecosystem integrity, including plant pollination and reproduction. In particular, invasive conifers (e.g., Pseudotsuga menziesii, Pinus spp.) escaped from forest plantations may impair seed production of anemophilous native conifers by altering the dynamics of wind-borne pollen flow among trees. In this study, we analyzed the effects of invasive conifers on the pollination and sexual reproduction of Andean cedar (Austrocedrus chilensis), a dioecious conifer native to the temperate forests of southern South America. Wind-dispersed pollen captured in pollen traps revealed that the timing of pollen release between the invasive and native conifers overlapped extensively, and the pollen cloud surrounding female cedar trees in invaded forest was heavily contaminated with pollen from the invasive conifers. Increasing abundance of invasive conifers in the proximity of female cedars decreased the local density of air-borne cedar pollen and increased contamination of the pollen cloud with pollen from the invasive conifers. This increased the chance of finding heterospecific pollen from these invaders in the micropyles of the native cedar. In turn, the presence of pollen grains from invasive conifers, particularly of P. menziesii, in the cedar’s micropyles was associated with a strong increase in the percentage of seed abortion. Our results clearly support the hypothesis that invasive conifers can interfere with the pollination and sexual reproduction of native wind-pollinated conifers. Thus, plantations of introduced and highly invasive conifers should not occur in the proximity of stands of native conifers in order to guarantee their reproduction and long-term population viability.

Climate refugia: from the Last Glacial Maximum to the twenty‐first century

Climate refugia: from the Last Glacial Maximum to the twenty‐first century

Illegal gene flow from transgenic creeping bentgrass: the saga continues

Ecologists have paid close attention to environmental effects that fitness-enhancing transgenes might have following crop-to-wild gene flow (e.g. Snow et al. 2003). For some crops, gene flow also can lead to legal problems,especially when government agencies have not approved transgenic events for unrestricted environmental release.Creeping bentgrass (Agrostis stolonifera), a common turf grass used in golf courses, is the focus of both areas of concern. In 2002, prior to expected deregulation (still pending), The Scotts Company planted creeping bentgrass with transgenic resistance to the herbicide glyphosate,also known as RoundUp, on 162 ha in a designated control area in central Oregon (Fig. 1).Despite efforts to restrict gene flow, wind-dispersed pollen carried transgenes to florets of local A. stolonifera and A. gigantea as far as 14 km away, and to sentinel plants placed as far as 21 km away (Watrud et al. 2004).Then, in August 2003, a strong wind event moved transgenic seeds from wind rows of cut bentgrass into nearby areas. The company’s efforts to kill all transgenic survivors in the area failed: feral glyphosate-resistant populations of A. stolonifera were found by Reichman et al.(2006), and 62% of 585 bentgrass plants had the telltale CP4 EPSPS transgene in 2006 (Zapiola et al. 2008; Fig. 2).Now, in this issue, the story gets even more interesting as Zapiola & Mallory-Smith (2012) describe a transgenic,intergeneric hybrid produced on a feral, transgenic creeping bentgrass plant that received pollen from Polypogon monspeliensis (rabbitfoot grass). Their finding raises a host of new questions about the prevalence and fitness of intergeneric hybrids, as well as how to evaluate the full extent of gene flow from transgenic crops.

Low genetic diversity and fragmentation effects in a wind-pollinated tree, Polylepis multijuga Plige (Rosaceae) in the high Andes

Fragmentation is predicted to increase inbreeding depression and lower the evolutionary potential of organisms by disrupting dispersal. Trees may be more resilient to fragmentation effects due to potential long-distance dispersal mechanisms that genetically connect fragments. Polylepis woodlands in the high Andes are highly fragmented and are currently the focus of reforestation and conservation efforts. Polylepis multijuga Plige (Rosaceae) is a threatened, endemic tree species in the northern Andes of Peru. Samples were collected from 371 adult trees in nine forest fragments separated by 0.5–80 km and genotyped at amplified fragment length polymorphism loci (AFLP) and chloroplast intergenic regions to determine the connectedness of fragments and their suitability for collecting seed for restoration efforts. P. multijuga is wind-pollinated and dispersed; however, genetic diversity in P. multijuga was about half that reported for other wind-pollinated species. Genetic spatial autocorrelation and patterns of chloroplast and AFLP diversity suggest seed dispersal is very limited and that wind dispersed pollen does not effectively connect all fragments. Conservation of this species will require reforestation efforts and possibly augmentation of some fragments to increase their genetic diversity. Collecting seed from multiple large fragments and from individuals separated by at least 25 m within fragments would maximize the genetic diversity of seed collections for reforestation or augmentation. Future studies of this and other Polylepis species should determine how complex topography may affect wind mediated dispersal between fragments and patterns of genetic diversity.

Petrographic approach to the study of organic microfossils from the Irati Subgroup (Permian, Paraná Basin, Brazil)

Early diagenetic chert, infrequently exploited in Phanerozoic micropaleontology, was examined for organic-walled microfossils in petrographic thin sections of silicified dolostones from diverse levels and localities of the Assistência Formation (Permian, Paraná Basin) in the state of São Paulo, Brazil. In contrast to previous palynological studies of this formation, the use of thin sections allowed direct observation in three dimensions of common palynomorphs, as well as benthic microbial mats preserved in situ in various stages of their life cycles and degradation. As in palynological residues from the more well-known shale of this formation, the chert contains wind-dispersed pollen grains and phytoclasts derived from terrestrial sources and planktonic cryptarchs (unornamented coccoidal unicellular or colonial palynomorphs). However, only in the chert is it possible to see much more delicate microfossils, such as abundant cyanobacteria of the in situ benthic microbiota as well as chlorophycean microalgae of the microphytoplankton. Post-depositional processes affecting the formation have destroyed all but the most resistant organic remains in the other lithologies, such that only rare, degraded pollen grains are seen in the unsilicified dolostone of the formation, and in the shale the vast majority of microfossils have been compacted to flattened disks. On the other hand, early silicification not only preserved organic remains at an incipient stage of decomposition but also impeded significant further degradation due to compaction, recrystallization, and oxidation. Thus, the petrographic study of such chert can complement traditional palynological investigations in Phanerozoic rocks by furnishing hitherto unavailable information, especially with regard to benthic organic microfossils and fragile organic-walled phytoplankton normally absent from organic residues.

Distribution and abundance of an allergenic weed, common ragweed (Ambrosia artemisiifolia L.), in rural settings of southern Quebec, Canada

Common ragweed (Ambrosia artemisiifolia L.) is an important weed of urban and rural settings in eastern Canada. Where the species is abundant, its wind-dispersed pollen is responsible for most cases of allergic rhinitis or “hayfever” in August and September. Despite its adverse health effects, there is little information on the actual abundance or distribution of ragweed plants in rural settings. Ragweed surveys were therefore done in July and August (after herbicide application) in corn and soybean fields, field borders and along rural roadsides surrounding two cities in southern Quebec. Based on zero-inflated Poisson regression models, ragweed density averaged 4.1 plants m-2 (Saint-Jean-sur-Richelieu area) and 16.1 plants m-2 (Salaberry-de-Valleyfield area) along roadsides. Ragweed density in field borders (1.3 plants m-2) and fields was lower than on roadsides. Conventionally tilled fields and fields where tillage was reduced had equivalent densities of ragweed. Ragweed abundance in fields was likely related to the efficacy of herbicides used in transgenic vs. conventional crops. Transgenic herbicide-resistant corn fields had higher ragweed densities than conventional fields (0.44 vs. 0.07 plants m-2), while herbicide-resistant soybean fields had lower densities than conventional fields (0.02 vs. 1.33 plants m-2). Field borders located closer to roadsides had slightly higher ragweed counts, while roadside densities did not depend on the proximity of a field entrance. This suggests that roadsides are currently potential sources of spread into fields more than the opposite. Further research on the pollen production and dispersal of these rural populations is needed.Key words: Weed density, corn, Zea mays, soybean, Glycine max, field border, field entrance, roadside, transgenic crops

Floral Scent Terpenoids Deter the Facultative FlorivoreMetrioptera bicolor(Ensifera, Tettigoniidae, Decticinae)

Non-pollinating florivores (animals feeding on floral resources) represent severe antagonists that have negative impacts on the plants' reproduction. Plants would thus benefit by excluding them from their flowers. In this study, we tested whether floral scent compounds that are attractive to many pollinators, also have the potential to prevent facultatively flower-feeding herbivores from consuming flowers. For feeding trials, we chose the bush cricket Metrioptera bicolor, a species that mainly consumes grasses, but also feeds occasionally on flowers. Linalool and β-caryophyllene (mono-and sesquiterpenoid, respectively) turned out to be effective antifeedants, while other floral scent compounds had no effect. Furthermore, bush crickets completely rejected flowers of Convolvulus arvensis (Convolvulaceae) and Melilotus alba (Fabaceae), while preferring flowers of Echium vulgare (Boraginaceae) over leaves. In addition to feeding experiments, excrement of bush crickets and other orthopterans were searched for pollen. Most individual bush crickets had pollen in their faeces, largely from Poaceae and Gymnosperms, suggesting accidental ingestion of wind-dispersed pollen, rather than targeted consumption of floral pollen. Our results support the hypothesis of a dual role of floral scents in attraction and defence.

Electrostatic forces in wind-pollination—Part 2: Simulations of pollen capture

During fair-weather conditions, a 100 V m −1 electric field exists between positive charge suspended in the air and negative charge distributed on the surfaces of plants and on the ground. The fields surrounding plants are highly complex reaching magnitudes up to 3×10 6 V m −1. These fields possibly influence the capture of charged wind-dispersed pollen grains. In this article, we model the electric fields around grounded conductive spherical “plants” and then estimate the forces and resulting trajectories of charged pollen grains approaching the plants. Pollen grain capture depends on many factors: the size, density, and charge of the pollen; the size and location of the plant reproductive structures; as well as wind speed, ambient electric field magnitude, and air viscosity. Electrostatic forces become increasingly important as pollen grain charge increases and pollen grain size (mass) decreases. A positively charged pollen grain is attracted to plants, while a negatively charged pollen grain is repelled. The model suggests that a pollen grain (10 μm radius, carrying a positive charge of 1 fC) is captured if passing within 2 mm of the plant. A similar negatively charged pollen grain is repelled and frequently uncapturable. The importance of electrostatic forces in pollen capture is limited by wind, becoming virtually irrelevant at high wind speeds (e.g. 10 m s −1). However, during light wind conditions (e.g. 1 m s −1), atmospheric electricity may be a significant factor in the capture of wind-dispersed pollen.

Electrostatic forces in wind-pollination—Part 1: Measurement of the electrostatic charge on pollen

Under fair weather conditions, a weak electric field exists between negative charge induced on the surface of plants and positive charge in the air. This field is magnified around points (e.g. stigmas) and can reach values up to 3×10 6 V m −1. If wind-dispersed pollen grains are electrically charged, the electrostatic force (which is the product of the pollen's charge and the electric field at the pollen's location) could influence pollen capture. In this article, we report measurements of the electrostatic charge carried by wind-dispersed pollen grains. Pollen charge was measured using an adaptation of the Millikan oil-drop experiment for seven anemophilous plants: Acer rubrum, Cedrus atlantica, Cedrus deodara, Juniperus virginiana, Pinus taeda, Plantago lanceolata and Ulmus alata. All species had charged pollen, some were positive others negative. The distributions (number of pollen grains as a function of charge) were bipolar and roughly centered about zero although some distributions were skewed towards positive charges. Most pollen carried small amounts of charge, 0.8 fC in magnitude, on average. A few carried charges up to 40 fC. For Juniperus, pollen charges were also measured in nature and these results concurred with those found in the laboratory. For nearly all charged pollen grains, the likelihood that electrostatics influence pollen capture is evident.

An unusual appearance of a common pollen type indicates the scene of the crime

Forensic palynology is a useful source of evidence in cases of violence committed in the open. A young girl was grabbed off the street, threatened and brutally raped. During the investigation the exact place of the rape became an issue. Growing around the scene identified by the victim were shrubs identified as Coprosma, a common New Zealand plant and one that produces abundant, easily wind-dispersed pollen. Abundant Coprosma pollen was found at the scene. The pollen were unusual in that the site was very damp, encouraging fungal growth, and fungal hyphae had penetrated the pores of many of the tricolporate pollen grains. Some grains had fungal spores inside. Coprosma pollen identical in preservational characteristics and morphology to those from the scene and containing fungal hyphae and spores were found in considerable numbers on the victim's clothes. This and rare Coprosma pollen grains and fungal remains recovered from vaginal swabs provided evidence that she had been at the scene where she claimed to have been raped. The diversity of pollen types recovered from the clothing in this case provides further evidence of the usefulness of clothing in picking up and retaining pollen from crime scenes and that obvious staining on clothes is not a pre-requisite for good pollen recovery. It also demonstrates the importance of collecting samples from different parts of the same garment in order to get a full picture of events since different parts of a garment can come into contact with different plants or different parts of the ground in a scuffle. It is also demonstrated that significant evidential material can be collected from the body, in this case from vaginal swabs from the victim. Forensic palynology should be considered in every case of violent assault, especially, but not exclusively, when having occurred in an open area subject to extensive pollen settlement.

Airborne Pollen and Fungal Spores in Florist Shops in Worcester and in Bristol, UK: A Potential Problem for Occupational Health

Persistent allergies are common in workers in florist shops but little research has been done on the reasons for this. This paper reports an investigation of occupational exposure of florists to pollen and spores in three florist shops over a 2-week period in the autumn of 2000. In each shop three sampling methods were used: Burkard continuous volumetric samplers, deposition plates and low-tac tape for surface samples, including hands of the florists and leaves of a selection of the plants. The florists kept a record of the type of work they undertook each day and of the stock amounts of flowers in the shops. The volumetric traps collected 80 pollen and spore taxa. The average concentrations recorded through the working day were generally low but short-term peak (one hour mean) concentrations of some types were found to be relatively high or very high. For a few taxa these concentrations equalled or exceeded those typical for short-term peaks in wind dispersed pollen types in the ambient air. Fungal spore concentrations of several known allergenic types were also very high for peak periods. This was most notable for Aspergillus spp. which reached extremely high concentrations in one shop, compared with typical peak concentrations in the ambient atmosphere. Low-tac tape leaf samples demonstrated that the flowers' foliage is a major source of the fungal spores. Few pollen grains or fungal spores were found on the hands.

Allometric gender allocation in Ambrosia Artemisiifolia (Asteraceae) has adaptive plasticity

Evidence is reported for size-dependent (allometric) gender allocation in the monoecious, wind-pollinated annual Ambrosia artemissifolia. Consistent with established theory, the pattern of allometry displayed adaptive plasticity, depending on the environmental cause of variation in plant size. Plant size gradients were generated in both field and greenhouse experiments using separate and combined gradients of shading, soil nutrient levels, and neighbor proximity. When plant size constraints involved light limitation from shading (e.g., because of close neighbor proximity), decreasing plant size was generally associated with decreasing maleness and increasing femaleness (based on relative male and female flower production, respectively). This is consistent with the "pollen-dispersal" hypothesis in which the consequences of relatively small plant size (among larger neighbors) imposes less severe limitation for female reproductive success than for male reproductive success (because success as an outcrossing donor of wind-dispersed pollen increases with increasing plant height, especially when neighbors are present). However, when size was constrained by soil nutrient limitation alone (i.e., without shading effects), the results had the converse allometric relationship; i.e., decreasing plant size was generally associated with increasing maleness and decreasing femaleness. This is consistent with the "size-advantage" and "time-limitation" hypotheses in which energetic and time limitations (respectively) associated with relatively small plant size impose a less severe limitation for male reproductive success than for female reproductive success.